Ultra violet stabilized polyolefins

ABSTRACT

Polyolefins stabilized against ultra violet light with nickel dialkyl dithiocarbamates and 2-hydroxy-4-octyloxybenzophenone.

United States Patent Edward Walter l-lussey Orange, Tex.

Feb. 1, 1970 Sept. 2 l, 1971 E. I. du Pont de Nemours and CompanyWilmington, Del.

Inventor Appl. No. Filed Patented Assignee ULTRA VIOLET STABILIZEDPOLYOLEFINS 6 Claims, No Drawings US. Cl 260/41 R, 260/41 B, 260/41 C,260/4575 N, 260/458 NZ, 260/4585, 260/4595, 260/897 A Int. Cl C08145/02, C08f 45/60 [50] Field of Search 260/4575 N, 45.95, 897 A, 45.85,45.8 N, 45.8 0, 41 B, 41 C Primary Examiner- Donald E. Czaja AssistantExaminer-V. P. Hoke Attorney-Earl L. Handley ABSTRACT: Polyolefinsstabilized against ultra violet light with nickel dialkyldithiocarbamates and 2-hydroxy-4-octyloxybenzophenone.

ULTRA VIOLET STABILIZED POLYOLEFINS This application is acontinuation-in-part of my copending application SER. NO. 637,361, filedon May 10, 1967 now abandoned.

invention relates to polyolefin composition stabilized with a mixture ofnickel dialkyl dithiocarbamate and 2-hydroxy-4- octyloxybenzophenone.

Nickel alkyl dithiocarbamate is a known additive to polyolefins for thepurpose of stabilizing the composition against ultra violet light. SeeBritish PAT. NO 889,690, issued June 13, 1962. 2hydroxy-4-octyloxybenzophenone is also a known additive to polyolefinsfor the purpose of stabilizing the compositions against ultra violetlight. See US. PAT. NO. 3,098,842, issued July 23, 1963.

It has now been found that if a nickel dialkyl dithiocarbamate is usedin combination with 2-hydr0zy-4 octyloxybenzophenone in a normally solidpolyolefin, the polyolefin is more stable against the effects of ultraviolet light than when the same total amount of either stabilizer isused alone. In other words, the combination acts synergistically tostabilize the polyolefin.

This synergistic activity is limited to nickel dialkyl dithiocarbamatesin which each alkyl group contains 4, 5, or 6 carbon atoms, when used incombination with only one hydroxybenzophenone compound, namely2-hydrozy-4-octyloxybenzophenone. The synergistic activity is alsolimited to combinations of these stabilizers in which the nickel dialkyldithiocarbamate is present in an amount on weight basis at least aboutequal to 50 percent of the combination and not more than about 95percent by weight of the combination. Stated on a weight ratio basis,the ratio of nickel dialkyl dithiocarbamate to2-hydroxy-4octyloxybenzophenone will vary from about 1:1 to 20:1. Theoptimum ratio will depend upon the presence or absence of othercomponents such as pigments, fillers and the like in the resin. Suchpigments and fillers are often added in amounts ranging up to 30 percentby weight of the composition. The optimum ratio will vary somewhatdepending on the particular color of the pigment employed. Pigmentedpolyolefin compositions are generally more ultra violet light stablethan nonpigmented polyolefin compositions.

This ultra violet light stabilizer combination may be used inconjunction with other types of stabilizers, for example, thermalstabilizers such as 2,6-ditertiary butyl-p-cresol; N-(phydroxphenyl)morpholine; tri-tert-butyl phenol;4,4'-butylidene-bis-(-tert-butyl-m-cresol); 2,2'-methylenebis (4-methyl-6-tert-butyl phenol); phenol); 2,4,6-tris-(3,5dimethyl-4-hydroxybenzyl) mesitylene; and dialkyl thiodipropionates such asdisclosed in Gribbins US. Pat. No. 2,519,755. These thermal stabilizersmay be used in amounts ranging from about 0.001 to about 1.0 percent byweight of the polyolefin. These thermal stabilizers do not affect theultra violet light stability of the compositions, but would be normallyadded to commercial resins to protect them during fabrication.

The total amount of stabilizer combination added may vary over widelimits; however, an amount in the range of about 0.0l to 1.0 percent byweight of the polyolefin is generally satisfactory for most uses. Anamount in the upper end of this range would be selected for maximum longterm stabilization.

The polyolefin stabilized by the combination can be any normally solidpolyethylene (branched or linear), polypropylene, copolymers of ethyleneand l-olefins of more than 2 carbon atoms, copolymers of propylene andl-olefins of more than 3 carbon atoms, as well as blends of thesepolyolefins with each other or other polymeric materials.

In the following examples which illustrate the invention all parts andpercentages are in parts by weight unless otherwise specified.

EXAMPLES I-lll A linear polyethylene homopolymer having a melt index of17.5 g/10 min. (ASTM D-1238-52T) and a density of 0.971 containing 225parts per million 2,6ditert-butyl-p-cresol and 0.04 percent MonastralGreen pigment, 0.18 percent cadmium yellow pigment, and 0.06 percenttitanium dioxide pigment and 0.1 percent by weight of the combination ofstabilizers in the ratios shown in the following table, was obtained byblending the ingredients on a 2-inch extruder at 180 C. Thereafter. theblended resin was injection molded into lids 0.055 inches thick fromwhich strips were cut for tensile testing. The strips were 3.5 incheslong and 2 inches wide. The strips were then exposed to an Atlas XWWeather-O-Meter with a Corex D filter. The exposure cycle was 18 minutesin water spray and 102 minutes dry at about 60 C. In accordance withASTM Method E-42-57.

The samples were removed from the Weather-O-Meter, dried, allowed tocome to equilibrium at 23 C. and then tested for tensile strength andelongation by ASTM Method D-l238-57-T. TheTable records the number ofhours it took for the samples to deteriorate to zero percent elongationTABLE 1 (Control 0.1% N BC)... '7 900 l ISO 1350 N BC is nickel dibutyldithiocarbamate HOBP is 2-hydroxy4-octyloxybenzophenone EXAMPLES [V VITest specimens of the same polyethylene resin as employed in examples 1lll were prepared with 0.25 percent (by weight) of the stabilizercombination in the ratios shown in the following table under theconditions of examples I --III except that no pigment was added, and thespecimens tested with the following results:

TA B LE 1 1 Ratio Time to 0% Example No. N BC /HOBP" Color Elongationlhr.)

(Control no stabilizer). I50 (Control .25% N BC) 3000 (Control 0.25%2000 HOBP).

*N BC is nickel dibutyl dithiocarbamate. HOBP is2-hydroxy-4-octyloxybenzophenone.

EXAMPLES VII-1X Test specimens of the same polyethylene resin asExamples I III were prepared with 0.5 percent of the combination ofstabilizers in the ratios shown in table 111 under the conditions shownin examples 1 lll, except that 0.04 percent Monastral Violet, 0.1 19percent Watchung Red B, 1.43 percent Molybdate Orange was added, and thespecimens were tested with the following results:

TAB LE 1 l 1 Ratio Time Example No. N BC*IHOBP" Color Elongation thr.)

(Control .5% NBC) 3000 7.. l 4000 8.. 3 4000 9.. 5 4000 *N BC is nickeldibutyl dithiocarbamate. HOBP is 2-hydroxy4-octyloxybenzophenone.

EXAMPLES X Xll ment .04 percent); Monastral Green pigment 0 .07 percent;and titanium dioxide 0.24 percent. The test results were as fol- TABLEIV Ratio Time to 0% I Example No. NBC*]HOBP** Elongation (hr) (Controlno stabilizer)... 210 (Control 0.25% NBC)... 3100 (Control 0.25% HOBP).2300 10 l 4000 e l 1.. 3 3500 12 r. 5 3300 EXAMPLES XIII XVIIl TABLE V 0Percent elon a Exam is of on No. Additive additive (hours) ControL Noadditive 140 Control. 2,6-ditert-butyl-pcresol 0. 02 150 13 "56955.251".

e u y -p-cres0 0.02 14 "{HOBP 1 0.1 15 NBC 0.1 900 0.02 --{NB 0.1 l

0.05 17 "IHOB 0.05 11175 Zfi-ditert-butyl-pcresol 0. 02 18 NBC l 0.05 l,150

HOBP 1 0. 05

1 NBC is nickel dibutyl dithiocarbamate. 1 H013? is2-hydroxy-4-0ctyloxybenzophenone.

EXAMPLES XIX XXIV Test specimens were prepared by blending on a rollmill at 165 C. a coordinate copolymer of ethylene and 0.20 percent byweight i-octene which had a melt index of 0.45 grams/ l0 with theadditives depicted in table VI in the concentrations depicted in tableVI, and then compression molding the blends into plaques 0.040 inchesthick, 3.5 inches long and 2 inches wide. The plaques were testedfollowing the procedure of example -III with the results indicated intable V1.

TABLE VI Time to 0% Percent oi a.

0 Example No. Additive additive (hours Control N0 additive 10 HOBP 0. 1600 0.1 l 6G0 006; 750 0% 01 05 l 0. 06 0. 05 850 0. 02

1 NBC is nickel dibutyl dithiocarbamate. l HOBP is2-hydroxy4-octyloxybenzophenone. I TDM is 2, 4, 6-tris-(3, fidirnethyl-4-hydroxybenzyl)mesitylene.

I claim:

1. A normally solid polyolefin composition containing as the polyolefina polymer selected from the group consisting of polyethylene,polypropylene, copolymers of ethylene and I- olefins of more than 2carbon atoms, copolymers of propylene and l-olefins of more than 3carbon atoms and blends thereof and a stabilizing amount of a mixture ofnickel dialkyl dithiocarbamate and 2-hydroxy-4-octyloxybenzophenone inwhich the alkyl groups of the nickel dialkyl dithiocarbamate contain 4to 6 carbon atoms and in which the weight ratio of nickel dialkyldithiocarbamate to 2-hydrozy-4-octyloxybenzophenone is within the rangeof about 1:1 to 201i 2. The composition of claim 1 in which thestabilizing amount is in the range of about 0 .01 percent to 1.0 percentby weight of the polyolefin.

3. The composition of claim 2 in which the alkyl groups on the nickeldialkyi dithiocarbamate are butyl groups.

4. The composition of claim 1 in which the polyolefin is selected fromthe class consisting of polyethylene and polypropylene and blendsthereof.

5. The composition of claim 2 which includes pigment.

6. The composition of claim I also containing thermal stabilizers.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3 ,fiO1 828I Dated qn'p rmnwn m 19:11

Inventor(s) EDWARD WALTER HUSSEY It is certified that error appears in'the above-identified patent and that said Letters Patent are herebycorrected as shown below:

Col. 2, lines 1,3 and t Specification 3000 patent 3000 3000 BOOO line 62#000 1,000

Signed and sealed this 1 1 th day of July 1 972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

1. A normally solid polyolefin composition containing as the polyolefina polymer selected from the group consisting of polyethylene,polypropylene, copolymers of ethylene and l-olefins of more than 2carbon atoms, copolymers of propylene and l-olefins of more than 3carbon atoms and blends thereof and a stabilizing amount of a mixture ofnickel dialkyl dithiocarbamate and 2-hydroxy-4-octyloxybenzophenone inwhich the alkyl groups of the nickel dialkyl dithiocarbamate contain 4to 6 carbon atoms and in which the weight ratio of nickel dialkyldithiocarbamate to 2-hydrozy-4-octyloxybenzophenone is within the rangeof about 1:1 to 20:1 .
 2. The composition of claim 1 in which thestabilizing amount is in the range of about 0 .01 percent to 1.0 percentby weight of the polyolefin.
 3. The composition of claim 2 in which thealkyl groups on the nickel dialkyl dithiocarbamate are butyl groups. 4.The composition of claim 1 in which the polyolefin is selected from theclass consisting of polyethylene and polypropylene and blends thereof.5. The composition of claim 2 which includes pigment.
 6. The compositionof claim 1 also containing thermal stabilizers.